firmware/dmi_scan: generalize for use by other archs

This patch makes a couple of changes to the SMBIOS/DMI scanning
code so it can be used on other archs (such as ARM and arm64):
(a) wrap the calls to ioremap()/iounmap(), this allows the use of a
flavor of ioremap() more suitable for random unaligned access;
(b) allow the non-EFI fallback probe into hardcoded physical address
0xF0000 to be disabled.

Signed-off-by: Ard Biesheuvel <[e-mail]>
Acked-by: Grant Likely <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc "Luck, Tony" <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/ia64/Kconfig

···
 config DMI
 	bool
 	default y
+	select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
 
 config EFI
 	bool

arch/ia64/include/asm/dmi.h

···
 #include <asm/io.h>
 
 /* Use normal IO mappings for DMI */
-#define dmi_ioremap ioremap
-#define dmi_iounmap(x,l) iounmap(x)
-#define dmi_alloc(l) kzalloc(l, GFP_ATOMIC)
+#define dmi_early_remap		ioremap
+#define dmi_early_unmap(x, l)	iounmap(x)
+#define dmi_remap		ioremap
+#define dmi_unmap		iounmap
+#define dmi_alloc(l)		kzalloc(l, GFP_ATOMIC)
 
 #endif

arch/x86/Kconfig

···
 # The code disables itself when not needed.
 config DMI
 	default y
+	select DMI_SCAN_MACHINE_NON_EFI_FALLBACK
 	bool "Enable DMI scanning" if EXPERT
 	---help---
 	  Enabled scanning of DMI to identify machine quirks. Say Y

arch/x86/include/asm/dmi.h

···
 }
 
 /* Use early IO mappings for DMI because it's initialized early */
-#define dmi_ioremap early_ioremap
-#define dmi_iounmap early_iounmap
+#define dmi_early_remap		early_ioremap
+#define dmi_early_unmap		early_iounmap
+#define dmi_remap		ioremap
+#define dmi_unmap		iounmap
 
 #endif /* _ASM_X86_DMI_H */

drivers/firmware/Kconfig

···
 	  under /sys/firmware/dmi when this option is enabled and
 	  loaded.
 
+config DMI_SCAN_MACHINE_NON_EFI_FALLBACK
+	bool
+
 config ISCSI_IBFT_FIND
 	bool "iSCSI Boot Firmware Table Attributes"
 	depends on X86

drivers/firmware/dmi_scan.c

···
 {
 	u8 *buf;
 
-	buf = dmi_ioremap(dmi_base, dmi_len);
+	buf = dmi_early_remap(dmi_base, dmi_len);
 	if (buf == NULL)
 		return -1;
 
···
 
 	add_device_randomness(buf, dmi_len);
 
-	dmi_iounmap(buf, dmi_len);
+	dmi_early_unmap(buf, dmi_len);
 	return 0;
 }
 
···
 		 * needed during early boot.  This also means we can
 		 * iounmap the space when we're done with it.
 		 */
-		p = dmi_ioremap(efi.smbios, 32);
+		p = dmi_early_remap(efi.smbios, 32);
 		if (p == NULL)
 			goto error;
 		memcpy_fromio(buf, p, 32);
-		dmi_iounmap(p, 32);
+		dmi_early_unmap(p, 32);
 
 		if (!dmi_present(buf)) {
 			dmi_available = 1;
 			goto out;
 		}
-	} else {
-		p = dmi_ioremap(0xF0000, 0x10000);
+	} else if (IS_ENABLED(CONFIG_DMI_SCAN_MACHINE_NON_EFI_FALLBACK)) {
+		p = dmi_early_remap(0xF0000, 0x10000);
 		if (p == NULL)
 			goto error;
 
···
 			memcpy_fromio(buf + 16, q, 16);
 			if (!dmi_present(buf)) {
 				dmi_available = 1;
-				dmi_iounmap(p, 0x10000);
+				dmi_early_unmap(p, 0x10000);
 				goto out;
 			}
 			memcpy(buf, buf + 16, 16);
 		}
-		dmi_iounmap(p, 0x10000);
+		dmi_early_unmap(p, 0x10000);
 	}
  error:
 	pr_info("DMI not present or invalid.\n");
···
 	if (!dmi_available)
 		return -1;
 
-	buf = ioremap(dmi_base, dmi_len);
+	buf = dmi_remap(dmi_base, dmi_len);
 	if (buf == NULL)
 		return -1;
 
 	dmi_table(buf, dmi_len, dmi_num, decode, private_data);
 
-	iounmap(buf);
+	dmi_unmap(buf);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(dmi_walk);